1. Field of the Invention
The invention relates to a switching element having a trench gate electrode and a manufacturing method thereof.
2. Description of Related Art Japanese Patent Application Publication No. 2009-117593 (JP-2009-117593 A) discloses a switching element having a trench gate electrode. In the switching element, an n-type source region, a p-type base region, and an n-type drift region are formed in a region in contact with a gate insulating film. In the switching element of this type, a high voltage tends to be applied to the gate insulating film at a portion interposed between the gate electrode and the drift region. Consequently, in the switching element, a p-type deep region is formed at a position below the base region that is not contact with the gate insulating film. When the high voltage is applied to the switching element, a depletion layer is formed to extend from the deep region toward the gate insulating film, and the application of a high electric field to the gate insulating film is thereby prevented.
The deep region of the switching element of JP-2009-117593 A is not a region where a main current flows. Therefore, when the deep region is formed in the switching element, there has been a concern that the switching element is increased in size though the value of a current that can be applied is not increased. Accordingly, the invention provides the switching element that is capable of preventing the application of the high electric field to the gate insulating film and is small in size, and a manufacturing method thereof.